[Boris]

I kept a G17 magazine loaded for 6.5 years. The magazine spring still felt new after I shot it and reloaded it. Its not really a matter of time. I go by rounds. My Glocks are my serious guns so I change them out every 5K per magazine. I shoot all my mags an equal amount so I will change out the springs on my G37 at 50,000 rounds, or about 12 years at the pace I am at right now......

edit: oops, I mean 25,000 rounds, or about 6 years. they have 2 years on them right now and still feel very strong........